A sequential inverse approach for hydraulic tomography and electrical resistivity tomography: An effective method for site characterization

Persistent Link:
http://hdl.handle.net/10150/279846
Title:
A sequential inverse approach for hydraulic tomography and electrical resistivity tomography: An effective method for site characterization
Author:
Liu, Shuyun
Issue Date:
2001
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Hydraulic tomography (i.e., a sequential aquifer test) has recently been proposed as a method for characterizing aquifer heterogeneity. In this study a sequential inverse approach is developed to interpret results of hydraulic tomography. The approach uses an iterative geostatistical inverse method to yield the effective hydraulic conductivity of an aquifer, conditioned on each set of head/discharge data. To efficiently include all the head/discharge data sets, a sequential conditioning method is employed. Two-dimensional numerical experiments were conducted to investigate the optimal sampling scheme for the hydraulic tomography. The effects of measurement errors and uncertainties in statistical parameters required by the inverse model were also investigated. The robustness of this inverse approach was demonstrated through its application to a hypothetical, three-dimensional, heterogeneous aquifer. Two sandbox experiments were conducted to evaluate the performance of the sequential geostatistical inverse approach under realistic conditions. One sandbox was packed with layered sands to represent a stratified aquifer while the other with discontinuous sand bodies of different shapes and sizes to represent a more complex and realistic heterogeneous aquifer. The tomography was found ineffective if abundant head measurements were collected at closely spaced intervals in a highly stratified aquifer. While it was found beneficial when head measurements were limited and the geological structure was discontinuous. The sequential inverse approach for hydraulic tomography was extended for electrical resistivity tomography. Numerical experiments were conducted to demonstrate the robustness of this approach for delineating the resistivity distribution in the subsurface and to investigate effectiveness of different sampling arrays of the ERT: the surface, the down-hole, and the combination of the surface and down-hole array. Orientation of bedding was found to dictate the effectiveness of the ERT layout. Samples were collected to quantify spatial variability of the resistivity-moisture relationship in the field. Numerical experiments then illustrated how the spatially varying relationship exacerbated the level of uncertainty in the interpretation of change of moisture content based on the estimated change in resistivity. A sequential inverse approach was then developed to estimate water content with less uncertainty by considering the spatial variability of the resistivity-moisture relationship and incorporating point moisture measurements and ERT data sets.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Geophysics.; Hydrology.; Environmental Sciences.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Hydrology and Water Resources
Degree Grantor:
University of Arizona
Advisor:
Yeh, T.-C. Jim

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleA sequential inverse approach for hydraulic tomography and electrical resistivity tomography: An effective method for site characterizationen_US
dc.creatorLiu, Shuyunen_US
dc.contributor.authorLiu, Shuyunen_US
dc.date.issued2001en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractHydraulic tomography (i.e., a sequential aquifer test) has recently been proposed as a method for characterizing aquifer heterogeneity. In this study a sequential inverse approach is developed to interpret results of hydraulic tomography. The approach uses an iterative geostatistical inverse method to yield the effective hydraulic conductivity of an aquifer, conditioned on each set of head/discharge data. To efficiently include all the head/discharge data sets, a sequential conditioning method is employed. Two-dimensional numerical experiments were conducted to investigate the optimal sampling scheme for the hydraulic tomography. The effects of measurement errors and uncertainties in statistical parameters required by the inverse model were also investigated. The robustness of this inverse approach was demonstrated through its application to a hypothetical, three-dimensional, heterogeneous aquifer. Two sandbox experiments were conducted to evaluate the performance of the sequential geostatistical inverse approach under realistic conditions. One sandbox was packed with layered sands to represent a stratified aquifer while the other with discontinuous sand bodies of different shapes and sizes to represent a more complex and realistic heterogeneous aquifer. The tomography was found ineffective if abundant head measurements were collected at closely spaced intervals in a highly stratified aquifer. While it was found beneficial when head measurements were limited and the geological structure was discontinuous. The sequential inverse approach for hydraulic tomography was extended for electrical resistivity tomography. Numerical experiments were conducted to demonstrate the robustness of this approach for delineating the resistivity distribution in the subsurface and to investigate effectiveness of different sampling arrays of the ERT: the surface, the down-hole, and the combination of the surface and down-hole array. Orientation of bedding was found to dictate the effectiveness of the ERT layout. Samples were collected to quantify spatial variability of the resistivity-moisture relationship in the field. Numerical experiments then illustrated how the spatially varying relationship exacerbated the level of uncertainty in the interpretation of change of moisture content based on the estimated change in resistivity. A sequential inverse approach was then developed to estimate water content with less uncertainty by considering the spatial variability of the resistivity-moisture relationship and incorporating point moisture measurements and ERT data sets.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectGeophysics.en_US
dc.subjectHydrology.en_US
dc.subjectEnvironmental Sciences.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineHydrology and Water Resourcesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorYeh, T.-C. Jimen_US
dc.identifier.proquest3031351en_US
dc.identifier.bibrecord.b42283176en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.